Add Gemini author and local icons for Claude, Codex, and Gemini

[Copilot]

Adds Gemini as a blog co-author alongside Claude and Codex, and replaces remote/fallback GitHub avatar lookups for all three with locally-hosted PNGs.

Icons

Downloaded 200×200 PNGs from official GitHub org avatars to docs/public/:

• claude.png — Anthropic org (u/76263028)
• codex.png — OpenAI org (u/14957082)
• gemini.png — Google org (u/1342004)

astro.config.mjs

• Added gemini author entry (https://gemini.google.com, /gh-aw/gemini.png)
• Pinned picture on claude and codex to local paths instead of relying on the https://github.com/${key}.png fallback

Usage

Any blog post can now reference all four AI co-authors:

authors:
- claude
- codex
- gemini
- copilot

Original prompt

Configure Astro author to include Claude, Codex, and Gemini. Decide on appropriate icons for each, download them for local use, and ensure they can be added as co-authors on any entry.

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[Copilot]

Pull request overview

This PR adds Gemini as a new blog co-author and replaces remote GitHub avatar lookups with locally-hosted PNG files for the three AI co-authors: Claude, Codex, and Gemini.

Changes:

• Added three 200×200 PNG avatar images downloaded from official GitHub organization profiles
• Updated author configuration to use local image paths instead of relying on remote GitHub avatars
• Added Gemini as a new available co-author alongside Claude, Codex, and Copilot

Reviewed changes

Copilot reviewed 1 out of 4 changed files in this pull request and generated no comments.

File	Description
docs/public/claude.png	Claude avatar image (200×200 PNG from Anthropic GitHub org)
docs/public/codex.png	Codex avatar image (200×200 PNG from OpenAI GitHub org)
docs/public/gemini.png	Gemini avatar image (200×200 PNG from Google GitHub org)
docs/astro.config.mjs	Added explicit picture paths for Claude and Codex, and new Gemini author entry

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